1. Field of the Invention
The present invention relates to a topography information data processing method for processing ground surface data which represents bumps and hollows on the ground surface and discrete geographic data that includes height information which indicates bumps and hollows on the ground and the like.
2. Description of Related Art
In recent years, as the computer becomes more sophisticated, the topography of the land and ocean floor is actively being transformed into database as exemplified by the concept of GIS (geographic information system). To obtain such database, the topography is expressed based on 3-dimensional geographic information data such as longitude, latitude, and height.
Geographic information data is obtained using sensor devices such as a satellite and an ultrasonic distance measuring equipment. These sensor devices measure the height or depth of each of observation points located on the ground in the form of grid points. Polygonal data and mesh data are acquired based on the 3-diemnsional geographic data obtained by measurement, that is, discrete geographic data. A surface which contains bumps and hollows on the ground is represented in a 3-dimensional space by carrying out rendering based on the polygonal data.
The amount of discrete geographic data obtained by the sensor devices is enormous. If the discrete geographic data is transformed into polygonal data, the amount of data increases even more. Therefore, it is difficult just to store the obtained enormous discrete geographic data and polygonal data. Currently, most of the discrete geographic data obtained by the satellites are discarded without being stored effectively.